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EFFECTS OF AMINOPYRALID HERBICIDES ON FORAGE BERMUDAGRASS YIELD

Applied Research

Brad Runsick
County Extension Agent - Agriculture
University of Arkansas System Division of Agriculture
Mountain Home

Abstract

Anecdotal evidence from county extension agents and farmers suggests that aminopyralid herbicides may reduce bermudagrass (Cynodon dactylon) forage yield. Those aminopyralid herbicides commonly used for broadleaf weed control include: GrazonNext HL, Milestone, Chaparral, and DuraCor. The purpose of this research is to determine the effects of varied rates of aminopyralid herbicides on forage yield. The on-farm research site was conducted in a 'Greenfield' bermudagrass hayfield. The site had a dense stand of bermudagrass with limited weed pressure to ensure reduced variability due to non-uniform forage growth and the reduced yield that would have occurred if broadleaf weeds were present.  Soil test results indicated the soil ph as well P and K were optimum. A standard treatment was included that contained 2,4-D amine, dicamba, and metsulfuron (Brash plus metsulfuron) to determine any lost yield due the reduction of broadleaf weeds. Treatments were randomized using a complete block design with 4 replications. Nitrogen was applied at 100 pounds per acre on June 16st, five days after the first hay cutting. Herbicides were applied June 24th, 13 days after the first hay cutting. Plots were harvested and forage dry matter yield was measured July 21st, 27 days after herbicide application. Yield response varied among the treatments. The 32 fl. oz/acre rate of GrazonNext HL reduced yield by 12% compared to the standard or control treatments (P<0.05). The forage yield did not differ between the control and all other treatments (P<0.05). To account for application accuracy, sprayer volumes were measured before and after application to determine actual active ingredient applied rates as compared to the intended rates. Further research is needed on other bermudagrass cultivars and in other environments. With the potential for high aminopyralid rates to affect bermudagrass yield, several implications can be a drawn: Sprayers should be properly calibrated. Weed populations should be at a threshold that necessitates an application. Use lower rates of aminopyralid if efficacy is the same for a particular weed species. Choose an alternative herbicide to aminopyralid if satisfactory control can be achieved.

Poster has NOT been presented at any previous NACAA AM/PIC

This poster is being submitted for judging. It will be displayed at the AM/PIC if not selected as a State winner. The abstract will be published in the proceedings.

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Authors: B. Runsick, K. Simon, C. Tyler, C. Stroud, D. Philipp
  1. Runsick, B. County Extension Agent - Agriculture, University of Arkansas System Division of Agriculture, Arkansas, 72653
  2. Simon, K. Program Associate - Forages, University of Arkansas System Division of Agriculture, Arkansas, 72204
  3. Tyler, C. County Extension Agent - Agriculture, University of Arkansas System Division of Agriculture, Arkansas, 72576
  4. Stroud, C. County Extension Agent - Agriculture, University of Arkansas System Division of Agriculture, Arkansas, 72513
  5. Philipp, D. Associate Professor, Animal Science, University of Arkansas System Division of Agriculture, Arkansas, 72701